"Just Like Heaven" is outlandish, uneven, preposterous and often maddeningly morbid.

And it features three shots of Mark Ruffalo getting out of the shower.

This featherweight romantic comedy starring Reese Witherspoon purveys the kind of fantastical fluff that, when skillfully handled, can make an otherwise forgettable chick flick a beloved middlebrow classic on a par with "When Harry Met Sally . . ." and "Sleepless in Seattle." Despite its strenuous attempts to pluck the same heartstrings, "Just Like Heaven" will never make that pantheon.

But it does feature three shots of Mark Ruffalo getting out of the shower.

That caveat means a lot to a certain subculture of mostly female filmgoers, who can generally be described -- or diagnosed -- as having a serious Mark Ruffalo Problem. Meaning: We -- sorry, they -- will see any movie Ruffalo is in, despite its artistic aspirations, redeeming social value, running time or degree of awfulness. If you have a Mark Ruffalo Problem, "You Can Count on Me" is as good as "In the Cut" is as good as "13 Going on 30" is as good as "We Don't Live Here Anymore."

And "Just Like Heaven" is very good indeed for MRP people, or even for less rabid fans of this gifted actor, who has proved his acting chops in such smart movies as "Eternal Sunshine of the Spotless Mind" and "Collateral" while carving out an unexpected but winning sideline as a romantic leading man, lending scruffy, thoroughly disarming charm to roles that usually call for the acting equivalent of Bachelor No. 2.

Here that role is to be a credible love interest for far-higher-wattage Witherspoon (just look at how they're portrayed on the movie's poster), and the chemistry works, largely because his understated sweetness plays so nicely against her preternaturally chirpy persona. When David Abbott (Ruffalo) moves into a fantastic San Francisco apartment and is immediately told to move out by its former tenant -- Elizabeth Martinson (Witherspoon), who three months earlier was hit head-on by a truck -- their banter crackles with tart, unforced verve. By now Elizabeth, a compulsively perky doctor, has become something of a tiresome stock character for Witherspoon, but here the prissy veneer is absorbed and softened by Ruffalo's low-key, unaffected magnetism.

As it becomes increasingly clear that Elizabeth isn't a real woman but a spirit visiting from another dimension, the comedy picks up even more, with some funny bits referencing earlier movies ("You're mopping that up," Elizabeth snaps after a priest scatters holy water during an exorcism), Jon Heder (the echt-nerd from "Napoleon Dynamite") spacily chewing the scenery as a psychic bookstore clerk and Ruffalo engaging in a bit of inspired physical comedy as the invisible Elizabeth tries to wrest a glass of Scotch from David's hands.

Indeed, as long as Elizabeth and David are trying to figure out what exactly happened to her, "Just Like Heaven" promises to be an inter-spiritual romance with the ethereal whimsy of such forebears as "Blithe Spirit" and "Heaven Can Wait" (as well as that movie's own forebear, "Here Comes Mr. Jordan").

But then they figure out what happened to her, and "Just Like Heaven" undergoes a radical shift in tone that gives it a ripped-from-the-headlines seriousness, raising troubling end-of-life issues that seem more at home in the pronouncements of Rep. Tom DeLay than a Saturday night date movie. Try as he might, director Mark Waters ("Mean Girls," "Freaky Friday"), working from an adaptation of a best-selling French novel called "If Only It Were True," can't quite thread the needle on this one. "Just Like Heaven" is a misfire, made all the more unsatisfying by a penultimate plot twist that beggars belief even by this movie's fantastical standards. (In another lamentable, if purely coincidental turn of events, one of the movie's supporting characters -- a voracious, predatory force of nature, as it happens -- is named Katrina.) Throw in a crass subtext regarding San Francisco's cutthroat real estate market and, despite some genuinely funny scenes and its sweet central relationship, "Just Like Heaven" turns into a bait-and-switch of a movie, wrapping weirdly maudlin speculation inside the candy coating of a frothy romance.

But it does feature three shots of Mark Ruffalo getting out of the shower.

Just Like Heaven (101 minutes, at area theaters) is rated PG-13 for some sexual content.